char* charset = " 0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
int charsetLength = strlen(charset);

std::string integerToKey(unsigned long long input)
{
    unsigned long long num = input;
    string key = "";

    while(num)
    {
        key += charset[num % charsetLength];
        num /= charsetLength;
    }

    return key;
}

// Create the integer to key conversion lookup table
int lookupChars;

if(lookupDisabled)
    lookupChars = 1;
else
    largeLookup ? lookupChars = 4 : lookupChars = 2;

lookupSize = pow(charsetLength, lookupChars);
integerToKeyLookup = new char*[lookupSize];

for(unsigned long i = 0; i < lookupSize; i++)
{
    unsigned long num = i;
    int j = 0;

    integerToKeyLookup[i] = new char[lookupChars];

    while(num)
    {
        integerToKeyLookup[i][j] = charset[num % charsetLength];
        num /= charsetLength;

        j++;
    }

    // Null terminate the string
    integerToKeyLookup[i][j] = '';
}

std::string integerToKey(unsigned long long input)
{
    unsigned long long num = input;
    string key = "";

    while(num)
    {
        key += integerToKeyLookup[num % lookupSize];
        num /= lookupSize;
    }

    return key;
}

const char* charset = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
#define CHARSET_LENGTH 62

// maximum size = 11 chars
void integerToKey(char result[13], unsigned long long input)
{
    char* p = result;
    while(input > 0)
    {
        *p++ = charset[input % CHARSET_LENGTH];
        input /= CHARSET_LENGTH;
    }

    // null termination
    *p = '';
    // need to reverse the output
    char* o = result;
    while(o + 1 < p)
        swap(*++o, *--p);
}

std::string ullToString(unsigned long long v, int base = 64) {
    assert(base < 65);
    assert(base > 1);
    static const char digits[]="0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ+/";
    const int max_length=65;
    static char buffer[max_length];

    buffer[max_length-1]=0;
    char *d = buffer + max_length-1;
    do {
        d--;
        int remainder = v % base;
        v /= base;
        *d = digits[remainder];
    } while(v>0);

    return d;
}

size_t base64_encode(char* outbuffer, size_t maxoutbuflen, const char* inbuffer, size_t inbuflen);

std::string integerToKey(unsigned long long input) {
    char buffer[14];
    size_t len = base64_encode(buffer, sizeof buffer, (const char*)&input, sizeof input);
    return std::string(buffer, len);
}